Multiple Adult Xanthogranuloma with Follicular Mucinosis-Associated Langherans Cell Histiocytosis

Langerhans cell histiocytosis and xanthogranuloma are both conditions characterized by increased histiocytic proliferation and are both more commonly seen in children. Nevertheless, the two are completely separate entities and have distinct differences in clinical presentation, histopathological appearance, prognosis, and therapy. Although adult forms of either disorder are rare, concurrent presentation of both is even more unusual. We report a 61-year-old man who presented with disseminated yellow-red papules coalescing into nodules, on a background of erythema and alopecia. Histopathology exhibited a dense dermal infiltrate of foamy histiocytes and lymphocytes in addition to follicular mucinosis with atypical folliculotropic cells. Appropriate staining revealed that the foamy histiocytes throughout the dermis represented a xanthogranulomatous process, while the folliculotropic proliferation represented Langerhans cell histiocytosis. Further work-up of this multiple adult xanthogranulomas with follicular mucinosis-associated Langerhans cell histiocytosis exposed underlying chronic myelogenous leukemia per bone marrow biopsy, which was likely either solely or partially an initiating factor in the eruption of multiple histiocytic process in this patient.